I run a small software studio in Bangkok. Last year a client asked us to help their HR team merge some PDFs. Payroll files. We told them to use one of the usual free sites, and their compliance officer said no. She was right. Those files were not allowed to leave the building. That is when I noticed the pattern. The people who need free file tools the most are the ones least allowed to use them. Accountants, HR, hospitals, law firms. Every tool in this category answers that with a promise: "we delete your file after two hours." A promise is not a control. So I built LightUtils around a constraint instead. The site sends a Content Security Policy with connect-src 'none'. That is a browser enforced rule saying this page may not make a network request, to anywhere, for any reason. Even if my own code tried to upload your file, the browser would refuse. Open DevTools, run a tool, watch the Network tab stay empty. The constraint made everything harder and better. No server means no ffmpeg, so trimming a video is hand-written MP4 parsing plus WebCodecs. No server means no cost per file, which is why there is no account, no watermark and no daily limit. It also forced me to care about memory: an early version of the batch image-to-PDF tool held every decoded bitmap and peaked at 1.5 GB of RAM. Now every batch tool processes one file at a time, and I measure the browser's process memory before shipping anything. It is bilingual, and the Thai is not a translated interface. Thai tone marks survive filenames, Thai CSVs that Excel turns into mojibake get repaired, Thai text sorts in dictionary order. Nothing else in this category bothers. 36 tools, zero dependencies, nothing collected. Happy to answer anything, especially if you try to break it.

LightUtils

36 file tools that physically cannot upload your files

36 file tools that physically cannot upload your files